This invention concerns a process for the synthesis of epsilon-caprolactam, henceforth "caprolactam" and an equipment particularly suited for realizing said synthesis.
In the usual plants caprolactam is obtained by reaction of cyclohexanone-oxime, henceforth "oxime", with an excess of oleum.
According to a first kind of process ("cold" process), the highly exothermal reaction is performed at a very low temperature (about -8.degree. C.), in the presence of liquid sulfur dioxide (which supplies refrigeration by means of evaporation), whereby there is obtained a sulfuric ester of caprolactam, having formula (I): ##STR1##
A second kind of process is residing in a "hot" process (in general at 40.degree. C.-150.degree. C.), in the absence of SO.sub.2, with the formation of a sulfuric ester of caprolactam, of formula (II): ##STR2##
The "cold" processes used so far showed the disadvantage of requiring excessive amounts of liquid SO.sub.2 (just for the purposes of refrigeration), but also the "hot" processes are showing drawbacks; if the temperature is very high, about 100.degree. C., the free SO.sub.2 content in the oleum must be relatively low (in general below 30% by weight) and the volumes of oleum are thus excessive.
The Applicant has now realized a process, henceforth "cold-hot process" or "mixed process", which allows to limit consistently all these drawbacks and which involves other considerable advantages, specified in more detail further on in the present description.